Nutrition & Performance · Research Brief · November 3, 2026
Carbohydrate fueling is getting more attention, but two small cycling trials show why a bigger hourly dose is not a universal performance prescription.
What happened after four hours
A randomized, double-blind crossover study published online October 7, 2026, in Medicine & Science in Sports & Exercise compared 60 and 100 grams of carbohydrate per hour in 15 trained male cyclists and triathletes. After a carbohydrate-rich day of eating, they completed four hours of cycling with intermittent hard efforts, followed by a 15-minute time trial.
The higher intake produced average time-trial power nine watts above the lower intake. Performance still declined from the fresh test in both conditions. Muscle biopsies did not show a significant difference in remaining muscle glycogen between the two fueling conditions. Better late-ride performance therefore should not be described as proof that the higher dose spared muscle glycogen. Read the study abstract.
Why more was not consistently better
A separate randomized study in the May 2026 issue of Scandinavian Journal of Medicine & Science in Sports tested 12 recreationally trained men. They completed rides of different intensities and durations with placebo, 40 grams of carbohydrate per hour, or 90 grams per hour, followed by a four-kilometer time trial.
After the 90-minute bout in the lower portion of the heavy-intensity range, the 40-gram condition improved time-trial performance compared with placebo. The 90-gram condition did not show that advantage. Neither dose significantly improved the time trial after the other two exercise protocols. Read the second study abstract.
Start with the session, not the biggest number
These experiments used different riders and exercise demands. Our editorial interpretation is that their results support context-specific fueling decisions, rather than a contest to consume the most carbohydrate. Both samples were small and male; neither establishes an optimal intake for every athlete or routine gym workout.
The NIH Office of Dietary Supplements places adequate food intake and hydration at the foundation of athletic performance. It notes that prolonged endurance activity can require additional carbohydrate, fluids, and electrolytes. Sports products can supplement that foundation; they do not replace it.
For your next conversation with a sports dietitian: describe the length and intensity of your training, your usual meals, and how your stomach responds during exercise. A study dose is a starting point for discussion, not an individual prescription.
Explore more Nutrition & Performance reporting.
Research & Sources
- Mazza and colleagues, 2026. Prolonged cycling and carbohydrate intake. DOI: 10.1249/MSS.0000000000004180.
- Fleitas-Paniagua and colleagues, 2026. Carbohydrate dose across cycling intensities. DOI: 10.1111/sms.70288.
- NIH Office of Dietary Supplements. Exercise and athletic performance fact sheet, accessed November 3, 2026.
Reporting is based on the published study abstracts and NIH guidance. General educational information; not individualized medical or nutrition advice.
